Session: 10.3.2 - Turbulent Flows II

Paper Number: 158598

158598 - Energy Transfer Mechanisms in Off-Axis Rotational Turbulence 

Abstract: 

Turbulent flows in rotational systems are crucial to understanding both large-scale phenomena, such as atmospheric and oceanic currents, and small-scale applications like flows in turbomachinery. While previous research has largely focused on the effects of rotation on mean flows and turbulent boundary layers, computational models adapted from inertial systems struggle to accurately capture the complexities of rotational turbulence, particularly in non-inertial reference frames where the standard Navier-Stokes (N-S) equations do not directly apply.  Consequently, a fundamental gap remains in our understanding of how rotation influences energy transfer mechanisms in turbulence, underscoring the need for further investigation and the development of models specifically designed for non-inertial rotational systems.

This study addresses this gap by analyzing energy transfer mechanisms in off-axis rotational coordinate systems. A cylindrical coordinate approximation is applied to accommodate the analysis for off-axis rotation condition to derive the N-S equations for cylindrical rotational coordinates. From these equations, we derive the turbulent kinetic energy (TKE) transport equations, focusing particularly on the turbulent component. Our analysis reveals a significant TKE transport term between radial and tangential directions, expressed as 2<u'_ru'_θ>Ω, which we term Coriolis Transport to emphasize the interplay between rotation effects and turbulence dynamics.

To understand the importance of the Coriolis transport introduced by rotation, the magnitude of the Coriolis transport is estimated using experimental data acquired by particle image velocimetry (PIV) from an experiment of co-rotate measurement of isotropic turbulence under the different off-axis rotation conditions. It is observed that Coriolis Transport keeps increasing with the Rossby number. It reaches 1/6 of dissipation rate as the turbulent Rossby number, defined as Ro_ε^-1, quantifying the rotational effect on the turbulence, increases to 5. This demonstrates that the Coriolis Transport plays a significant role in the energy budget of the off-axis rotational turbulent flow and helps to explain the anisotropy found in energy spectra resulting from experiments between the radial and tangential directions.

Presenting Author: Yijie Wang Purdue University

Presenting Author Biography: